PURPOSE: To provide a motor-driven tool which can make rapid progress in the surface processing capability for a plate piece, and improve the reduction to a compact size, energy saving and operability by remarkably improving the prior art.

CONSTITUTION: A motor-driven polisher 1, as shown in Fig. 1, has a driving motor 1b built in an insulating body 1a and a grip 1c and a switch 1d which are provided on the lower area. A torque converting mechanism 2 for converting the turning torque of the motor 1b to the reciprocating torque and a buff 3 for applying wax or the like to the surface of an automobile or the like are fitted to the front of the body 1 through a driving shaft 3a.